This invention relates generally to dispergers for removing contaminants from recycled, or recovered, paper and packaging materials. More particularly, the present invention relates to disperger plate segments for use in such apparatus.
Recovered paper and packaging materials are subjected to several processes designed to remove ink, toner in the case of copy paper, and contaminants such as plastics generally referred to as “stickies”. The removal processes are not completely efficient and the residual ink, toner and stickies must be dispersed or else the stickies adhere to parts of the paper machine and cause holes or weak spots in new paper. Residual ink particles appear as specs in the reconstituted paper lowering its value considerably.
A machine called a disperger is used to reduce the size of the ink and stickie particles so that in subsequent paper machine operations paper qualities are minimally impacted. The general configuration of this machine is two circular discs facing each other with one disc (rotor) being rotated at up to 1800 rpm. The other disc is stationary (stator). On the faces of the discs are mounted plate segments having pyramids or teeth mounted in tangential rows. The rows are at radii chosen to allow the rotor and stator pyramids to intersect the plane between the discs so that the fiber passing from the center of the stator to the periphery of the discs must receive impacts from the rotor pyramids as they pass close to the stator pyramids. The clearance between rotor and stator pyramids is on the order of 1 to 12 mm so that the fibers are not cut but severely and alternately flexed. This action breaks the ink and toner particles into smaller particles and also breaks the stickie particles and it is thought that the fresh sticky surfaces collect fine fiber particles and are further passivated as smaller particles. Increasing the number of flexures the fibers experience has been shown to improve the particle reduction process. Adding more pyramids generally improves the efficiency of the dispersion process but the size of the pyramids that can be manufactured at reasonable costs limits this number.